A headlamp is a lamp usually attached to the front of a vehicle such as a car, with the purpose of illuminating the road ahead during periods of low visibility, such as darkness or precipitation. Headlamp performance has steadily improved throughout the automobile age, spurred by the great disparity between daytime and nighttime traffic fatalities. The U.S. National highway Traffic Safety Administration has indicated that nearly half of all traffic-related fatalities occur in the dark, despite only 25% of traffic traveling during darkness. Varghese, Cheman; Shankar, Umesh (May 2007). Passenger Vehicle Occupant Fatalities by Day and Night—A Contrast; Traffic Safety Facts, Research Note (DOT HS 810 637) (NHTSA's National Center for Statistics and Analysis) http:www-nrd.nhsta.dot.gov/Pubs/810637.pdf. While it is common for the term headlight to be used interchangeably in informal discussion, headlamp is the technically correct term for the device itself, while headlight properly refers to the beam of light produced and distributed by the device.
In the beginning, there were no headlamps for horseless carriages or automobiles. When the early adopters of the horseless carriage had to drive at night, they did the same thing that regular carriages did, hang a kerosene lantern on the front of their vehicle. The earliest headlamps were fueled by acetylene or oil and were introduced in the late 1880s. Acetylene lamps were popular because the flame was resistant to wind and rain.
This was not an ideal solution, so people began experimenting with electric headlamps. The first electric headlamps were introduced in 1898. Two factors limited the widespread use of electric headlamps: the short life of filaments in the harsh automotive environment, and the difficulty of producing dynamos small enough, yet powerful enough to produce sufficient current. Georgano, G. N. (2002). Cars: Early and Vintage, 1886-1930 (A World of Wheels Series, Mason Crest. Peerless made electrical headlamps standard in 1908. When mounted to the vehicle, these lamps were aimed straight forward at that time.
In 1912, Cadillac integrated their vehicle's Delco electrical ignition and lighting system, creating the modern vehicle electrical system and in 1917, Cadillac began selling cars with “dipping” headlamps, which could be angled via a lever to point towards the ground in front of the car. Eventually, these two aiming positions became known as “low beams” and “high beams”. The situation has not changed much since then, with all cars having both low and high beams, with nothing in between, despite the lack of evidence that only two lighting positions is ideal. In a study funded by the NHTSA, it was found that people had trouble quickly choosing and switching between more than two positions. There is currently a push in the industry towards implementing headlamp technology that will intelligently and automatically control the switching to provide effective, middle distance lighting.
In contrast to the stagnation in the evolution of how headlamps are used, the technology behind them has changed dramatically since the dawn of the twentieth century. Automobile manufacturers went from using acetylene or oil-filled lanterns to incandescent bulbs to halogen bulbs to the current state-of-the-art, High Intensity Discharge (also called HID or Xenon) lamps and LEDs. For each different technology, different methods of making the switch between low and high beams had to be invented. The general method, as shown in FIG. 1, used with HID lamps is to have a solenoid-activated lever or a motor-activated mechanism physically move a metal shield into the path of the light beam, blocking the portion that would exit the top of the lamp, thereby “turning off” the high beams.
There is found in JP publication No. 2007-250327 and in U.S. Pat. No. 7,575,353 (its US counterpart), a lighting device that includes a light shielding plate being configured to impart a required or desired light distribution pattern by shielding light received directly from a light source and/or light reflected from a reflector. The movement of the light shielding plate is achieved by rotation about a vertical rotary shaft. In an embodiment of the described invention, the light shielding plate is a drum-type movable light shielding plate.
There is found in JP Publication No. 2009-266758, a double object headlight that emits light with a cutoff, in particular a low beam as a first function and emits a high beam as a second function. Such a headlight includes a pull-in type shade plate capable of taking an operation position for low beam emission and a pull-in position for high beam emission. The upper edge for the cutoff is located in the vicinity of the focal point of the lens at the operation position. In the pull-in position, the upper edge of the cutoff is located in a lower part of the reflecting mirror when the shade plate is rotated to the front side to function as a reflecting surface and thus contribute to the emission of the high beam.
There is found in Korean Publication No. 1020091031481, a shield for a vehicle headlamp having an inclined surface in the end portion of protrusions. The shield includes a vertical surface in the outer side of the protrusions so as to facilitate the separation of the mold after manufacturing of the shield is completed. The main body of the shield is pivotally installed and includes a protrusion is provided in the main body to block a part of light coming from the light source.
There also is shown in FIGS. 3A, B a cross-sectional schematic view of a headlamp for a Lincoln MKS. In FIG. 3A, the headlamp is shown configured for low beam operation where the shield is disposed so as to block a portion of the light coming from the light source and/or reflected from the reflector. The headlamp when configured for high beam operation is shown in FIG. 3B. When in high beam operation, the shield is rotated or moved so to be tipped in a forward direction and so it is no longer in the path of emanating light beam.
The use of a rotating shield such as shown in FIGS. 1 and 3 works, however, it is far from ideal. The chief shortcoming of such a rotating shield is its lack of flexibility. Because the rules governing headlamp patterns are different in the United States than in the rest of the world, auto manufacturers have to make different styles of headlamps for the United States, Europe and Asia, as well as different headlamps for left- or right-sided driving. Further such mechanisms are not readily adaptable to provide mid-distance lighting.
In general, headlamps presently in use are electrically operated and form a headlamp system where the headlamps are positioned in pairs, one or two headlamps on each side of the front of a vehicle. Such a headlamp system for a vehicle is required to produce a low and a high beam, which may be achieved either by an individual lamp for each function or by a single multifunction lamp.
High beams (also called “main beams” or “full beams” or “driving beams” in some countries) cast most of their light straight ahead, maximizing the seeing distance, but producing too much glare for safe use when other vehicles are present on the road. Also, because there is no special control of upward light, high beams also cause back dazzle from fog, rain and snow due to the retroreflection of the water droplets. Low beams (called “dipped beams” in some countries) have stricter control of upward light, and direct most of their light downward and either rightward (in right-traffic countries) or leftward (in left-traffic countries), to provide safe forward visibility without excessive glare or back dazzle.
Low beam (dipped beam, passing beam, meeting beam) headlamps provide a distribution of light designed to provide adequate forward and lateral illumination with limits on light directed towards the eyes of other road users, to control glare. This beam is intended for use whenever other vehicles are present ahead. The International ECE Regulations for filament headlamps and for high-intensity discharge headlamps specify a beam with a sharp, asymmetric cutoff preventing significant amounts of light from being cast into the eyes of drivers of preceding or oncoming cars. Control of glare is less strict in the North American SAE beam standard contained in FMVSS/CMVSS 108.
Most low-beam headlamps are specifically designed for use on only one side of the road. Headlamps for use in left-traffic countries have low-beam headlamps that “dip to the left”; the light is distributed with a downward/leftward bias to show the driver the road and signs ahead without blinding oncoming traffic. Headlamps for right-traffic countries have low beams that “dip to the right”, with most of their light directed downward/rightward.
Within Europe, when driving a vehicle with right hand (RH) traffic headlamps in a left hand (LH) traffic country or vice versa for a limited time (as for example on vacation or in transit), it is a legal requirement to adjust the headlamps temporarily so that the wrong-side hot spot of the beam does not dazzle oncoming drivers. This may be achieved by adhering blackout strips or plastic prismatic lenses to a designated part of the lens. Many tungsten (pre-halogen) European-code headlamps made in France by Cibié, Marchal, and Ducellier could be adjusted to produce either a left- or a right-traffic low beam by means of a two-position bulb holder. More recently, some projector-type headlamps can be made to produce a proper left- or right-traffic beam by shifting a lever or other movable element in or on the lamp assembly. Because wrong-side-of-road headlamps blind oncoming drivers and do not adequately light the driver's way, and blackout strips and adhesive prismatic lenses reduce the safety performance of the headlamps, most countries require all vehicles registered or used on a permanent or semi-permanent basis within the country to be equipped with headlamps designed for the correct traffic-handedness.
As to HID lamps and with reference also to FIG. 1, HID lamps produce light from a millimeter-sized electric arc passing through a compressed mixture of xenon and metal halide gases contained in a light bulb or capsule. Because the light-generating region is so small, it can be placed at one focus of an elliptical reflector. Due to the geometry of an ellipse, all of the light will be concentrated at the second focus of the ellipse, (approximately where the movable plate is located). Past the second focus, the light continues to expand until it passes through lens (e.g., a convex lens), which gives the light beam its final shape.
HID lamps produce more light for a given level of power consumption than the halogen lamp technology they can displace. They also produce a different spectrum of emitted light, some of which is in the near infrared range, which results in significant heating of materials directly in the path of a concentrated beam of light. An illustrative spectrum of emitted light for an HID lamp is shown in FIG. 2.
Automotive HID lamps are commonly called “xenon headlamps”, though they are actually metal halide lamps that contain xenon gas. The xenon gas allows the lamps to produce minimally adequate light immediately upon power up, and accelerates the lamps' run-up time. If argon were used instead, as is commonly done in street lights and other stationary metal halide lamp applications, it would take several minutes for the lamps to reach their full output. The light from HID headlamps exhibits a distinct bluish tint when compared with tungsten-filament headlamps.
HID headlamp bulbs do not run on low-voltage DC current, so they require a ballast with either an internal or external igniter. The ballast controls the current to the bulb. Typically, the ignition and ballast operation proceeds in three stages. Also, HID headlamp burners produce between 2,800 and 3,500 lumens using from between 35 and 38 watts of electrical power, while halogen filament headlamp bulbs produce between 700 and 2,100 lumens using from between 40 and 72 watts. The reduced power consumption means less fuel consumption, with resultant less CO2 emission per vehicle fitted with HID lighting.
If the higher-output HID light source is used in a well-engineered headlamp optic, the driver gets more usable light. Studies have demonstrated drivers react faster and more accurately to roadway obstacles with good HID headlamps rather than halogen ones. The contrary argument is that HID headlamps can negatively impact the vision of oncoming traffic due to their high intensity and “flashing” effect due to the rapid transition between low and high illumination in the field of illumination, thus increasing the risk of a head-on collision between the HID-enabled vehicle and a blinded oncoming driver.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.
It thus would be desirable to provide a multi-functional projector lamp shield and a multi-functional projector embodying such a shield. It would be particularly desirable to provide such a multi-functional lamp shield device and a multi-functional projector embodying such a shield where the shield is not movable such as by mechanical devices such as those required when using prior art shields. It also would be desirable to provide such a multi-functional shield and multi-functional lamp that can be easily adapted for use with different types of vehicles and differing regulatory requirements.